Circuits for electric discharge devices



May 24, 1932. H. 5. BLACK 1,859,494

' .CIRCUI'rs FOR ELECTRIC DISCHARGE DEVICES Filed Feb. 28. 1927 Patented May 24, 1932 UNITED STATES PATENT a t *a. "5.

HAROLD s. BLACK, or EAST ORANGE, NEW JERsEmssxsnoR 'ro WESTERN nancrnro COMPANY, INCORPORATED, OF NEW YORK, 1L, ACORPORATION OF NEW YORK CIRCUITS FOR ELECTRIC DISCHARGE DEVICES Application filed February 28, 1927. Serial No. 171,582.

This invention relatesto circuits for elec-- tric discharge devices and in particular to balanced or push-pull circuits.

An object of the invention is to improve the operation of such circuits, and particu larly to increase the etficiency of their operation. I

When the cathodes of two devices connected in a balanced or push-pull circuit are connected in series to a source of heating current they will be at different potentials with respect to their respective grids. This difference in grid potentials tends to produce'an unbalance of the currents in the output circuits which is often undesirable. .Heretofore, such unbalances have been prevented by the use of separatesources of grid biasing potential or by the use of impedance networks in the output circuits. Under many circumstances either method of compensation has decided disadvantages. For example it is often preferable to employ a singlesource of grid biasing potential and the latter method of compensation is inefficient since it introduces a loss in the output circuit of one device.

In accordance with this invention there is provided an output transformer having its primary winding adjusted to compensate for unbalances in the circuits of the two devices.

This invention is particularly Well suited for use in a balanced self-oscillating modulating or detecting circuit of the type de-' scribed in applicants copending application, Serial No. 58,744, filed September 26, 1925,

*i Patent No. 1,653,837, grantedDecember 27,

1927. In this type of circuit a resistance is employed in the grid-cathode circuit for giving a grid biasing potential due to the po-' tential drop produced by current flowing in the grid circuit, and oscillations are set up by means of a connection from the output circuit to the input circuit. When the cathodes of the two devices are heated in series and a single resistance is employed for giving the biasing potential, dissimilarity of operation results, one device functioning in the conventional manner as a self-excited oscil-' lator and the other operating in parallel as a non-oscillatory regenerative amplifier. Such operation is desirable, and in accordance this" invention the primary windings of the output transformer are adjusted; to produce equal effects on the secondary, thus compensating for the differences in out-I put currents to prevent the transmission of the generated carrier wave to the load circuit. 7

panyingdrawings in which: Fig. 1 shows diagrammatically an embodiment of the invention in a frequency translating circuit employing a separate source of carrier, and Fig. 2 shows an embodiment of the invention in a self-oscillating frequency translating circuit.

Fig. 1 shows a balanced frequency translatlng circuit of the general type described in U. S. Patent No. 1,343,306, granted to J. R. Carson, June 15, 1920. Two electric discharge devices 4 and 5 are connected in balanced relation between an input transformer 6 and an output transformer 17. The cathodes of the devices are connected in series to receive heating current from a di- The invention is illustrated in the accom rect current source 8. Space current is sup plied to the devices from a source 9, a blocking condenser 10 and a retardation coil 11 supplied to the input circuit and transmit the combination products to the. load circuit through the output, transformer 17 in the manner described in Patent No. 1,343,306, referred to above. When the circuits of the two devices 4 and 5 are balanced,the carrier wave supplied to the input circuit will not appear in the load circuit. However, the

series cathode heating circuit tends to produce an unbalance in the operation of the two dev1ces,s1nce the potential of the cathode The circuit operates to combine the waves of one device with respect to its grid varies from that of the other device by an amount equal to the potential drop across one cathode. This tends toproduce an unbalancein the output currents of the two devices. With the circuit arrangement shown the potential of the grid of the device will be more negative with respect to its cathode than the potential' of the grid of the device 4 with respect to its cathode, so that the current flowing in the output circuit of the device 5 will be lower than that flowing in the output circuit'of the device 4. Inorder to compensate for this effect the primary winding 14 of the output transformer 17 is designed to have more turns than the primary winding so that the ampere turns produced by the windings will be equal and both will produce the same effect on the secondary winding. While the differencein grid potentials is the controlling factor there will also be a slight difference in the anode potentials, similarly produced by the series cathode heating circuit. If desir able, the effect of this potentialdifference may be simultaneously compensated by properly proportioning the windings 14 and 15.

Figure 2 shows a'balanced self-oscillating frequency translatingcircuit of the type described in applicants Patent No. 1,653,837, referred to above. In this circuit two electric discharge devices 20 and 21 are connected in push-pull relation between an input transformer 22 and an output transformer 23 The cathodes of the two devices are connected in series to receive heating current from a battery 24. Space current is supplied from a battery 25 connected in series with the retardation coil 26. The common plate connection is made from the primary of the output transformer 28 through a tuned feed-back circuit 27 and a blocking condenser 28 to the cathodes of the devices. The cathodes are also connected through resistance 29 and 0011- denser 30, in parallel, and the coil 31, induc tively associated with the tuned feed-back circuit 27, to the mid-point of the secondary.

winding of the input transformer 22.

The circuit is so operated that during a portion of each cycle current flows in the grid circuit producing a potential drop across the The efiect of the series cathode heating circuit is to make the biasing potential of'the two devices different, resulting in dissymmetrlcal operatlon. In general the difference 1n grid potentials is suchthat when the circuit,

is arranged to provide a steady negative biasing potential through the operation of the resistance 29, the grid of device 21 fails to become positive at any point in the cycle.

This means that the device 20 performs the biasing and stabilizing function for both de-- and Condenser perform the respective functions of stabilizing the operation of the circuit and preventing'grid current modulation. i r

Similarly to the circuit of Figure 1, the primary windings 32 and33 of the output transformer 23 are so adjusted with respect to each other that they both have the same ampere turn value and so-produce the same effect on the secondary'winding, thus preventing the transmission of any generated carrierto the load circuit. The effect is such that when no signal wave-is impressed upon the input transformer 22 no current will How in the secondary windings of the output transformer 23.

What is claimed is:

1. A balanced vcircuit comprising two electric discharge devices, 'each having a cathode and an anode, means for supplying heating current to said cathodes inserles, and an output transformer having a primary winding connected to the cathode and anode of each of said devices and a secondary windin'g, said primary windings being adjusted to produce equal effects on'said secondary winding to. compensate for the imbalance produced by the series cathode heating circuit.

2. A balanced circuit comprising two electric discharge devices, each having a cathode, an anode anda grid, a circuit for supplying heating current to said cathodes in series, a load circuit, and an output transformer havinga primary winding connected to the oathode and anode of each of said devices, said windings beingadjusted to'compensate for the difference in the grid potential of said devices produced by the series cathode heat-.

ing circuit to produce equal efiects in the load circuit. i

3. A balanced frequency translating cir cuit comprising two electric discharge devices each having a cathode, an anode and a control electrode, a circuit for supplying heating current to said cathodes in series, an in-,

put circuit having a common portion connected to said cathodes and an individual portion connected to each'of said control elec-' trodes, means for supplying'waves of different characteristics to said common and individual portions, and an output transformer having a primary winding connected to the anodeand cathodeof each of said devices pensate for the unbalance produced by the series cathode heating circuit and eliminate the Waves supplied to said common input portion. 1

4. A self-oscillatory frequency translating circuit comprising a pair of electric discharge devices each having a cathode, an anode and a control electrode, a circuit for supplying heating currentto said cathodes in series, an input circuit having a common portion connected to said cathodes and an individual portion connected to each of said control electrodes, means for impressing Waves on said individual portions, an output circuit having a common portion connected to said cathodes and an individual portion connected to each of said anodes, a feed-back circuit containing frequency determining means connecting said common output and input portions, a resistance in the common input portion of such value With respect to the feed-back that the control electrode of one of the devices periodically goes positive during normal operation by an amount sufficient to provide a normal negative bias for both of said devices, and an outputttransformer having a primary Winding connected in each of said individual output portions and a secondary Winding, said primary Windings being adjusted to produce equal effects on said secondary Winding to compensate for the difference in the biasing potentials pro duced by the series cathode heating circuit so that when no Wave is impressed on said individual input portions no voltage is induced in said secondary Winding.

In Witness whereof, I hereunto subscribe my name this 17th day of February A. D.,

HAROLD S. BLACK. 

